Calipers or dividers



L. S. STARRETT.

GALIPERS 0R DIVIDERS.

(No Model.)

No. 411,537. Patented Sept. 24, 1889.

- firmly against the adj Listing-nut.

UNTTED STATES PATENT @EETCE.

LAROY S. STARRETT, OF ATIIOL, MASSACIIUSETTS.

CALIPERS OR DIVIDERS.

SPECIFICATION forming part of Letters Patent No. 411,537, datedSeptember 24, 18-89.

1 Application filed May 4, 1889. $erial No.309,685. (N0 model.)

' iliary-milled nut upon the brace between the arms, in position for theadjusting-spring to bear against, instead of said spring acting directlyon a solid shoulder of the brace, as heretofore. The object of thisfeature of construction is to admit of pressing back the spring byturning said auxiliary nut, after the fine adjustment has been made, theauxiliary nut then looking the spring and arm The spring may be either aflat one, riveted to the inner face of the arm, as is commonly used, ora spiral spring encircling the brace and seated in a chambered cavity inthe arm, which is the preferred form.

My second improvement includes a stud set in a recess in the other arm,perforated for passage of the wing or brace, such stud having a threadedprolongation to receive the binding thumb-nut.

These novel features are hereinafter described, and specified in theappendedclaims.

I11 the drawings, Figure l is a plan of dividers embodying myimprovements, and

showing, also, caliper-legs to be substituted for the divider-legs. Fig.2 is a section through the head and arms of the instrument in the planeof the curved wing. Fig. 3 is a perspective detail of the stud detached,and Fig. 4 a detail of the locking-nut with a flat adjusting-spring.

A B represent the arms of the instrument pivoted to each other at theirupper ends and furnished with interchangeable legs and arms 0, heldiirlongitudinal recesses of the arms by a clamping-ring D and nut E. Thearms are connected near their upper ends by an arc-shaped wing, eitherof the usual flat form or ofa form circular in cross-section, the latterbeing preferable.

Figs]. and 2 represent the wing F as a round rod threaded at one end,where it passes loosely through the arm A to receive the ad justing-nutG outside the arm and the lockingnut H between the arms. Said figuresalso show a coiled spring J surrounding this rod and seated in a recessin the arm A, into which it may be compressed by the movement of eithernut. The advantage of this construction is that the instrument may bedelicately set or adjusted by the nut G against the springpressure, andthen looked fast in the desired position by screwing up the locking-nutII until it bears firmly against the inside of the armA, pressing thespring J into the chambered seat. lVhen a flat spring I is employed, asin Fig. 4, it presses back flat against the arm. This remedies the weakpoint in wing-dividers, which have heretofore been no stiffer than theadjusting-spring. With myimprovement, the arms, when locked, areperfectly rigid, whether the chambered, spiral, or the plain flat springis used. This result can only be attained by securing the arm B firmlyto the brace or wing F. Heretofore the flat wing has been used and asetscrew bore by its point against the fiat side thereof, the straincoming always on two or three threads of such screw. I set a stud K inthe leg B, perforate it, as at L, Fig. 3, to receive the wing-rod F, andfurnish its projecting stem with a long screw-thread M to receive athumb-nut N of corresponding length. By tightening this thumb-screw thewing is clamped firmly, the perforated stud drawing it firmly into closecontact with the wall of the aperture through the arm.

I claim as my invention 1. In dividers or calipers, the pivot-ed arms,provided with a connecting wing or brace and an external adjustingnut,in combination With a spring adapted to be compressed by said nut, andwith a locking-nut between the arms for holding the parts firmly whenadjusted, substantially as set forth.

2. In dividers or calipers, the pivoted arms A B and the brace or wingF, passing through both arms and secured to one by a suitable clamp, incombination with the nuts G H,

screwing upon the threaded end of said Wing, and with the coil-spring J,surrounding said Wing and compressible between said nuts into a recessin the leg A, substantially as set forth.

3. In dividers or calipers, the pivoted arms, the arc-shaped wingcircular in cross section, passing transversely through them, and anadjusting-nut, in combination with a stud set IO in a recess in the armB and perforated for passage of the Wing through it, and provided with athreaded stem and athuinb-nut thereon for clamping the arm in position,substantially as set forth.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing Witnesses, on this 6th day of April,

LAROY S. STARRETT. WVitnesses:

HENRY R. VAILLE, HENRY M. BURLEIGH.

